The REM latencies of 24 nonschizotypal borderline outpatients--who were not in the midst of a major depressive episode--were in the range of those of 30 patients with primary major depression but were significantly shorter than those of 16 patients with nonborderline personality disorders and 14 nonpsychiatric controls. Also, more of the borderline subjects had lifetime diagnoses of affective disorder, such as dysthymic, cyclothymic, and bipolar II disorder, and of a spectrum of anxiety and somatization disorders. The authors conclude that contemporary operational criteria for borderline disorder identify a wide net of temperamental disorders with strong affective coloring rather than a unitary nosologic entity.